where \(P_{(ch,i )}\)  is the channel power, \(P_{(ASE,i)}\)  is the ASE noise within the channel bandwidth, \(P_{(s-s,i)}\)  and \(P_(s-n,i)\)  are the NLI noise power arising from signal-signal and signal-noise nonlinear interactions, respectively. Details on the calculation from Eq. (REF ) can be found in [1]}, [2]}.
